Japanese Utility Model Publication No. H07-15186 and Japanese Patent Application Laid-Open No. 2002-118633 disclose an opening/closing apparatus for an equipment case, in which a transmission case and a reception case for a portable cellular telephone set are turnably connected to each other through a two-axis hinge apparatus. In this opening/closing apparatus, a transmission case is turnably connected to one end part of a hinge main body of a two-axis hinge apparatus through a first hinge shaft, and a reception case is turnably connected to the other end part of the hinge main body through a second hinge shaft. Owing to this arrangement, the reception case and the transmission case are turnably connected to each other through an opening/closing apparatus.
In the above-mentioned conventional opening/closing apparatus for an equipment case, since the transmission case and the reception case are merely turnably connected to a hinge main body through first and second hinge shafts, a determination cannot be made as to whether the reception case is turned with respect to the hinge main body or the hinge main body is turned with respect to the transmission case when the reception case is to be turned with respect to the transmission case. In other words, no turning order is firmly established between the reception case and the hinge main body. Therefore, the turning order between the reception case and the hinge main body is changed every time the reception case is turned with respect to the transmission case. This gives rise to a user having a sense of uncomfortability.